Guest Blog: 5G and SD-WAN Inside Out and Outside In

By Tom Nolle
| April 26, 2019

Everyone is interested in 5G these days, including both users of SD-WAN services and operators looking to integrate SD-WAN with 5G. Most 5G stories deal with the carrier’s view of the technology, but users will never see those details. They’ll see only the services 5G can bring them. 128 Technology already has a nice blog on the operator or “inside-out” perspective of 5G and SD-WAN.

I’m going to focus on the “outside-in” 5G service features that enterprises will see, and how 128 Technology’s implementation of SD-WAN optimizes those service features, using explicit connectivity, session awareness, and session-based policy routing.

The biggest service difference between 5G and 4G is bandwidth. Mobile 5G is expected to offer two to five times the speed of 4G, and the “millimeter-wave” version of 5G designed to replace wireline delivery to homes and small business sites could offer ten to fifty times the speed of today’s copper-wire broadband. For many branch offices and small sites, 5G could become the fastest network technology available, and that could change how SD-WAN is used both as a backup to wireline and as a replacement for it.

For many branch offices and small sites, 5G could become the fastest network technology available, and that could change how SD-WAN is used both as a backup to wireline and as a replacement for it.

Small-site backup using 4G isn’t common, but it’s happening. What 5G brings is a backup option that’s more realistic, more likely to sustain operations in affected locations. That doesn’t mean it’s identical, either in pricing or in cost, or that failing over to backup won’t create a disruption in itself. That’s one area where your SD-WAN implementation can make or break your connectivity strategy.

When a connection fails, the applications using it will normally see the disruption and fail as well. Tunnel-based SD-WAN may have to re-establish the tunnels as well as the sessions over them, and the combination can create a protracted outage. 128 Technology doesn’t use tunnels, and because it recognizes each authorized session individually, it can recover the session paths to reduce or even eliminate the secondary failures that can disrupt operations. The no-tunnel approach also reduces SD-WAN overhead on backup links where bandwidth is limited or where you pay data usage charges.

128 Technology doesn’t use tunnels, and because it recognizes each authorized session individually, it can recover the session paths to reduce or even eliminate the secondary failures that can disrupt operations.

Another backup challenge that’s largely unrecognized is the change in traffic routing that usually accompanies a failover. Both wireline and 5G access connect to the Internet and then to the company VPN. The two access options may involve different network operators, different traffic gateways, and thus will connect to the corporate VPN in a different place. The “optimum” path between the office whose connection has failed over and the applications and resources being used may well change, and if that change isn’t recognized, it’s likely to generate additional application latency and even traffic congestion.

With session-based policy routing, the path authorized sessions take is constantly monitored and adapted to changes in conditions. If after backup is established for a broadband connection, the best path for a given application to take goes through a different set of SD-WAN nodes, a new route will be selected automatically, based on policies established by the SD-WAN user. Configuration of the SD-WAN will adapt to the new access connections.

With session-based policy routing, the path authorized sessions take is constantly monitored and adapted to changes in conditions.

Policies are also important when you consider the fact that backup 5G connections may not be as fast as wireline, or may incur additional charges. Prioritization of traffic by “type” is helpful, but every CIO knows that all phone or video calls, all access to applications, don’t have the same level of business importance even though traffic types may be the same. With individual session awareness, users can set meaningful priorities based not only on the application, but on who’s accessing it or even when it’s being accessed. That means that scarce backup capacity can be assigned where it does the most good. The same mechanism can throttle traffic representing non-critical use, such as web-surfing, to reduce charges incurred during backup operation.

With individual session awareness, users can set meaningful priorities based not only on the application, but on who’s accessing it or even when it’s being accessed. That means that scarce backup capacity can be assigned where it does the most good.

These mechanisms can also be applied where 5G is the primary site access option, to accommodate the variable capacity and latency often found in mobile networks subject to variable load. As 5G access conditions change, these changes can trigger changes in prioritization, in how some application traffic is routed, and in whether low-priority traffic is admitted at all.

Another 5G service feature that should impact your consideration of SD-WAN features and vendors is the impact of machine-to-machine (M2M) or the Internet of Things (IoT). It’s not likely that enterprises will install SD-WAN nodes on each of their IoT sensors, but 5G support for IoT is very likely to result in many new sites, sites where there may be no permanent staff to connect but where IoT controllers are gathering information and making process or facility changes. Some industries, particularly utilities, could use 5G to network two to ten times the number of sites they network today.

All these new sites can create a major problem for some SD-WAN implementations. Most tunnel-overlay SD-WAN technology has a fixed limit on the number of tunnel connections, often in the thousands. With 128 Technology, there’s support for millions of session connections, enough to support not only a widely distributed workforce but also a large population of IoT device communities.

With 128 Technology, there’s support for millions of session connections, enough to support not only a widely distributed workforce but also a large population of IoT device communities.

5G IoT also reopens the point about route and traffic control by application session. 5G is designed to be a low-latency network technology to improve event-handling, but having low-latency access does little good if the events are held up because of congestion or inefficient routing within the SD-WAN and company VPN. Explicit connection management by logical name, combined with explicit session-aware routing and continuous monitoring of QoS, means users can minimize latency within their SD-WAN and into the corporate VPN or cloud to reach applications.

Because most SD-WANs will have multiple paths to reach the company VPN and applications, picking the optimum one is important. The “best” path for events may be different from the best path for normal transaction traffic because the various QoS parameters are traded in different ways. QoS routing by application and parameter means that applications sensitive to latency or “jitter” in delay can be routed to minimize or avoid those problems.

5G will open more sites to SD-WAN as well as open new and more useful backup opportunities, but 5G is more than just plugging in a 5G modem. It’s important that these benefits be preserved by accommodating 5G’s specific capabilities in the SD-WAN you use to connect these sites. If you don’t your investment in 5G service, and in SD-WAN, could be at risk.

Tom Nolle is president of CIMI Corporation, a strategic consulting firm specializing in telecommunications and data communications since 1982.